Activation of an Essential Calcium Signaling Pathway in Saccharomyces cerevisiae by Kch1 and Kch2, Putative Low-Affinity Potassium Transporters

Yeast Fex1p Is a Constitutively Expressed Fluoride Channel with Functional Asymmetry of Its Two Homologous Domains

“…For the patch clamp measurements, ϳ5 l of suspension was pipetted into the recording chamber, allowed to settle for ϳ10 min, and then flushed with a stream of standard recording buffer (Buffer D: 150 mM KCl, 10 mM CaCl 2 , 5 mM MgCl 2 , 1 mM MES, pH 7.5), to remove debris and nonadherent cells. Slightly alkaline buffers were used throughout the measurements for three explicit reasons as follows: (i) to suppress spurious movement of fluoride via HF, the undissociated acid (pK a ϭ 3.2); (ii) to suppress fluxes of inorganic cations via Kch1,2p and other nonselective "channels" through the yeast plasma membrane (31,32); and (iii) to minimize confusing halide conductance facilitated by the TRK1 and TRK2 K ϩ transporters (29). Visibly clean protoplasts of ϳ8 m diameter were selected under bright field illumination (ϫ400) and picked by the patch pipette, using suction at ϳ8 cm of H 2 O.…”

Reciprocal Regulation of Target of Rapamycin Complex 1 and Potassium Accumulation

“…Some studies suggest that a channel activity denominated NSC1 is responsible, but this channel has yet to be characterized at the molecular level (45,46). Other candidates for these uptake systems include nonspecific uptake by the Qdr2 drug/H ϩ antiporter, glucose permeases, and the Kch1 and Kch2 (Prm6) potassium transporter proteins (47)(48)(49)(50).…”

Kch1 Family Proteins Mediate Essential Responses to Endoplasmic Reticulum Stresses in the Yeasts Saccharomyces cerevisiae and Candida albicans

“…On the other hand, two putative K ϩ transporters, Kch1 and Kch2, were recently shown to regulate HACS through the transportation of extracellular K ϩ , suggesting regulation through changes in the membrane potential (34). Expression of Kch1 and particularly Kch2 was strongly induced by the response to mating pheromones, which resulted in activated HACS, Cn, and cell survival mechanisms during prolonged mating responses (34).…”

“…2ϩ Uptake and CN Activation in S. cerevisiae Cells Exposed to Tunicamycin-The activation of HACS during the response to mating pheromones was recently shown to depend on the related fungus-specific proteins Kch1 and Kch2 (34). To test whether Kch1 and Kch2 are required for the activation of HACS during a very different kind of stress, ER stress, the uptake of 45 Ca 2ϩ was measured in kch1 kch2 double mutants and single mutants during a 4-h exposure to tunicamycin in the presence of FK506, an inhibitor of Cn that relieves the feedback inhibition of HACS.…”